SEO Optimization images is becoming more and more important in SEO (Search Engine Optimization) for websites. The ALT attribute is a critical step that is sometimes forgotten. This is often a lost chance of better rankings.
In Google's webmaster guidelines, they advise using alternative text for that images on your site:
Images:. Use the alt attribute to supply descriptive text. In addition, we recommend utilizing a human-readable caption and descriptive text round the image.
Why would they ask us to do that? The answer is easy, really; search engines have the same problem as blind users. They can't begin to see the images.
Many webmasters and inexperienced or unethical SEOs abuse using this attribute, attempting to stuff it with keywords, looking to achieve a certain keyword density, which isn't as relevant for rankings now since it was previously.
On the other hand, high keyword density can, on some search engines, trigger spam filters, which might result in a penalty for your site's ranking. Even without this type of penalty, your site's rankings won't benefit from this tactic.
This process also puts persons who use screen readers at a greater disadvantage. Screen readers are software-based tools that actually read aloud the contents of what is displayed on the screen. In browsing the web, the alt features of images are read aloud as well.
Imagine hearing a paragraph of text that is followed by repetitions of many keywords. The page would be far from accessible, and, to put it mildly, will be found quite annoying.
What is an Alt attribute?
An ALT attribute should not be used like a description or perhaps a label for an image, though lots of people utilize it for the reason that fashion. Though it may appear natural to assume that alternate text is really a label or perhaps a description, it's not!
The words used within an image's alt attribute should be its text equivalent and convey exactly the same information or serve the same purpose the image would.
The thing would be to provide the same functional information that the visual user would see. The alt attribute text should function as a "stand in" in the event that the look itself is not available. Think about this question: Should you replace the image using the text, would most users receive the same basic information, and wouldn't it generate the same response?
Some examples:
If your search button is a magnifying glass or binoculars its alt text should be 'search' or 'find' not 'magnifying glass' or 'binoculars'.
If an image is meant to convey the literal contents of the look, a description is suitable.
If it is meant to convey data, then that data is what is appropriate.
If it's designed to convey using a function, then the function is what should be used.
Some Alt Attribute Guidelines:
Always add alt attributes to images. Alt is mandatory for accessibility as well as for valid XHTML.
For images that play merely a decorative role within the page, use an empty alt (i.e. alt="") or a CSS background image so that reading browsers don't bother users by uttering such things as "spacer image".
Remember that it is the function of the image we are trying to convey. For example; any button images shouldn't include the word "button" in the alt text. They ought to emphasize the action performed by the button.
Alt text should be based on context. The same image in a different context may need drastically different alt text.
Try to flow alt text with the rest from the text because that's how it will be read with adaptive technologies like screen readers. Someone listening to your page should hardly be aware that a graphic image is there.
Please keep in mind that utilizing an alt attribute for every image is required to satisfy the minimum WAI requirements, that are used as the benchmark for accessibility laws in UK and also the rest of Europe. Also, they are required to meet "Section 508" accessibility requirements in the US.
It is important to categorize non-text content into three levels:
Eye-Candy
Mood-Setting
Content and Function
I. Eye-Candy
Eye-Candy are things that serve no purpose other than to create a site visually appealing/attractive and (oftentimes) fulfill the marketing departments. There isn't any content value (though there may be value to a sighted user).
Never alt-ify eye-candy unless there is something there that will enhance the usability from the site for someone utilizing a non-visual user agent. Use a null alt attribute or background images in CSS for eye-candy.
II. Mood-Setting
This is the middle layer of graphics which might actually set the atmosphere or set the stage so to speak. These graphics aren't direct content and may not be considered essential, but they're important in they help frame what's going on.
Try to alt-ify the second group as makes sense and is relevant. There might be times when doing this might be annoying or detrimental with other users. Then avoid it.
For example; Alt text that's identical to adjacent text is unnecessary, and an irritant to screen reader users. I recommend alt="" or background CSS images in such instances. But sometimes, it's important to get this content inside for those users.
Most times this will depend on context. Exactly the same image in a different context may need drastically different alt text. Obviously, content ought to always be fully available. How you use this case is a judgment call.
III. Content and Function
This is when the look may be the actual content. Always alt-ify content and functional images. Title and long description attributes can also be in order.
The reason many authors can't understand why their alt text isn't working is they don't know why the pictures exist. You have to determined precisely what function an image serves. Consider what it's about the image that's important to the page's intended audience.
Every graphic includes a reason behind being on that page: since it either improves the theme/ mood/ atmosphere or it is advisable to what are the page is trying to explain. Knowing what the image is perfect for makes alt text simpler to write. And practice writing them definitely helps.
A method to check the usefulness of alternative text is to imagine reading the page on the phone to someone. An amount you say when encountering a particular image to make the page understandable towards the listener?
Aside from the alt attribute you've got a couple more tools available for images.
First, in degree of descriptiveness title is within between alt and longdesc. It adds useful information and can add flavor. The title attribute is optionally rendered by the user agent. Remember they are invisible and not shown as a "tooltip" when focus is received via the keyboard. (A lot for device independence). So make use of the title attribute only for advisory information.
Second, the longdesc attribute points to the URL of a complete description of an image. If the information contained in a picture is essential towards the meaning of the page (i.e. some important content would be lost when the image was removed), a longer description than the "alt" attribute can reasonably display ought to be used. It can provide for rich, expressive documentation of a visual image.
It ought to be used when alt and title are insufficient to embody the visual qualities of the image. As Clark [1] states, "A longdesc is a long description of the image...The goal is to use any period of description essential to impart the facts from the graphic.
It wouldn't be remiss to hope that a long description conjures a picture - the image - in the mind's eye, an analogy that holds true even for the totally blind."
Although the alt attribute is mandatory for web accessibility as well as for valid (X)HTML, not all images need alternative text, long descriptions, or titles.
Oftentimes, you are best just choosing your gut instinct -- if it's not necessary to include it, and when you don't possess a strong urge to do it, don't add that longdesc.
However, if it's essential for the whole page to operate, then you have to add the alt text (or title or longdesc).
What's necessary and what's not depends a great deal about the function of the image and its context on the page.
The same image may need alt text (or title or longdesc) in a single spot, but not in another. If an image provides absolutely no content or functional information alt="" or background CSS images may be appropriate to make use of. But if the image provides content or adds functional information an alt would be required and maybe even a long description will be so as. In many cases this kind of thing is really a judgement call.
Listed here are key stages in optimizing images:
Choose a logical file name that reinforces the keywords. You should use hyphens in the file name to isolate the keyword, but avoid to exceeding two hyphens. Stay away from underscores like a word separator, like for example "brilliant-diamonds.jpg";
Label the file extension. For example, when the image search engine sees a ".jpg" (JPEG) file extension, it's likely to assume the file is really a photo, and when it sees a ".gif" (GIF) file extension, it's likely to assume that it is a graphic;
Ensure that the text nearby the image that is highly relevant to that image.
Again, don't lose a great chance to help your site together with your images in search engines. Begin using these steps to position better on all of the engines and drive increased traffic to your site TODAY.
Peter Risdon Says:
May 16, 2011 at 2:40 pm | Reply
The paragraph you quoted from ends with this sentence:
“According to the best-sited stations, the diurnal temperature range in the lower 48 states has no century-scale trend.”
That was a surprise given the tenor of this post: “… maybe this is the end to questions as to whether surface temperature increases actually exist.”
Did you mean that we can now say the answer to that is that surface temperature increases do not exist? Or that, pace Keenan in the WSJ, the data do not contain statistically significant trends?
andyrussell Says:
May 16, 2011 at 2:58 pm | Reply
I don’t think diurnal temperature range is very important. Do you?
What’s more, the “century-scale” bit covers some interesting detail. Before Fall et al., it seems that the only work on diurnal temperature range showed a negative trend from the mid-century to 1980s-ish. What Fall et al. found was that this has increased again since the 1980s. So there’s no “century-scale trend”.
But that tells you very little about mean surface temperature trends.
Mark Says:
May 17, 2011 at 10:45 pm
I have heard it claimed that the reduction in diurnal temperature range over the past few decades provides evidence that GHG increases are responsible for the warming. In that sense, some people think diurnal temperature range is important.
Incidentally, I don’t think Fall et al. were the first to find that DTR has increased since the 1980s. I read a paper that said much the same thing a few years ago.
Sorry for the lack of references to back up these statements. I’m a little too busy at the moment to chase them up.
Ben Says:
May 16, 2011 at 4:49 pm | Reply
So Peter… If the diurnal high and the diurnal low both rise by 1°C, you think this means there has been no warming? After-all, the diurnal range hasn’t changed! Others might draw a different conclusion.
Peter Risdon Says:
May 17, 2011 at 8:26 am | Reply
I understand diurnal range has significance, and the relationship between day and night time temperature ranges is important, especially with regard to the period 1950 to 1980 when the effect of man-made global warming, it has been argued, was masked by a cooling but revealed by the changes in the relationship between these ranges.
I further understand that this argument is based on the idea that human pollution caused this daytime cooling, that it affected the range of day time temperatures as well as the difference between night time temperatures which continued to show warming, and daytime ones that didn’t. This makes day time temperature range significant: if this is right it would be expected to show a variation that correlates with human activity.
But this isn’t my field; I’m just reading what I can in an attempt to understand as much as possible about an important issue and, for me at least, that means reading Watts and reading this blog. Just searching out stuff you’re already disposed to accept isn’t good enough. My comment was prompted by what struck me as a somewhat partial quotation and exasperation: I’m with Feynman when he said you should point out the problems with a theory, not just the things that support it.
[It's not really a "partial quotation" is it? That sentence you are interested in is stuck on the end of the abstract as a new paragraph and isn't really related to the 2 sentences I quote and which are related to the subject of this post. I'm not really interested in DTR and I doubt Watts was either. - AR]
At least Watts invites people with different views to post on his blog and has been at the forefront of attempts to cross the ideological divide, not least with Judith Curry.
Ben, of course you’re right. Andy, a century is an arbitrary scale, of course.
I’d still be interested in your take on statistical significance.
JMurphy Says:
May 17, 2011 at 12:05 pm | Reply
In what way has Watts atempted to cross “the ideological divide” ?
Ben Says:
May 17, 2011 at 3:16 pm | Reply
Peter, I encourage a critical (i.e. thoughtful) reading of Anthony’s blog but my god do you really think he’s “at the forefront of attempts to cross the ideological divide”? Anthony has done more to harden denialist thought than anyone, with the possible exception Marc Morano.
The “different views” he solicits are unthreatening fig-leaves.
andyrussell Says:
May 17, 2011 at 3:24 pm | Reply
I’ve got no problem with most of what Keenan says, although he’s not the first/only person to be saying these things. There’s a JoC paper from 2010 and it was one of the useful points to come out of the UEA email enquiries (i.e. working more with stats people). Not sure where the funding was supposed to come from for these new people though!
I suppose the bigger problem comes down to climate science covering so much stuff – you can’t just look at problems from a stats/dynamics/modelling/chemistry/radiation/whatever perspective for too long before a) not getting very far or b) needing to doing something you’ve not done before.